The company have a special business process is: Customers ordering a
product, a Sale Order was created, Booked and waiting for pick release. But
sometimes ,the customer want receive the invoices before the delivery.to y make
a Manual Invoice and reference the Invoice to that Sale Order for tracking
progress shipping later. Because the invoice was Manual then may be variance
between the invoice and total shipped goods.

Solution:
we can map to custom report (like Delivery Challan/Order) having
similar looks like Invoice which will be called thru a request set, at the
time of pick release. However,

based on
actual delivery invoice was generated and said custom report number was
shown as a reference. Legal implications of local tax authorities also
need to ensure.